The so called "simulcast" methodology currently favored by the Federal Communications Commission, involves transmitting a conventional television signal, for example NTSC, over a first television channel, and transmitting a high definition television (HDTV) signal over an additional channel which would be assigned to each broadcaster. Since the assignment of an additional channel to each broadcaster will involve the use of those channels currently designated as "taboo" channels (i.e. those restricted for use in a given location), use of those channels requires that a way be found to prevent, or minimize within acceptable limits, the interference caused by or attributable to these additional broadcast signals with respect to the existing conventional signals.
The copending parent U.S. application No. 614,885 referred to above, describes an embodiment of a multicarrier television signal having a particular advantage in that it minimizes co-channel interference with conventional transmissions. The embodiment of the HDS/NA-6 signal described in the parent application features the placing of its multiple subcarriers within the frequency spectrum of its channel bandwidth, so as to avoid the high energy video and chroma subcarriers present in a conventional (i.e. NTSC) signal occupying the same channel in a nearby city, in other words a "taboo" channel. Although this embodiment featured an analog approach to the signal configuration, the application also discussed a digital embodiment of the invention. The instant application represents an embodiment of such a digital configuration.
It is therefore an object of the instant invention to provide a method and apparatus for implementing a digital television signal which will eliminate, or minimize to acceptable levels, interference to a conventional television signal present in a related television channel.
It is another object of the invention to provide a digital signal which is least affected by the conventional television signal.
It is yet another object of the invention to provide a method and apparatus for encoding a digital multicarrier signal in a manner which provides optimum protection against co-channel interference.
It is a still further object of the invention to provide a method and apparatus for decoding the digital signal and providing an HDTV display.